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First map of Zika virus could speed vaccine hunt

Friday, Apr 1, 2016,14:03 IST By Metrovaartha A A A

Washington | Scientists, including one of Indian-origin, have for the first time determined the structure of the Zika virus, a breakthrough that may help develop effective vaccines for the mosquito-borne virus which has been linked to serious birth defects.

A team led by Purdue University researchers identified regions within the Zika virus structure where it differs from other flaviviruses, the family of viruses to which Zika belongs that includes dengue, West Nile, yellow fever, Japanese encephalitis and tick-borne encephalitic viruses.

Any regions within the virus structure unique to Zika have the potential to explain differences in how a virus is transmitted and how it manifests as a disease, said Richard Kuhn, who led the research team that includes Purdue graduate student Devika Sirohi.

The structure of the virus provides a map that shows potential regions of the virus that could be targeted by a therapeutic treatment, used to create an effective vaccine or to improve our ability to diagnose and distinguish Zika infection from that of other related viruses, said Kuhn. Determining the structure greatly advances our understanding of Zika – a virus about which little is known, he said.

The Zika virus, a mosquito-borne disease, has recently been associated with a birth defect called microcephaly that causes brain damage and an abnormally small head in babies born to mothers infected during pregnancy. It also has been linked to the autoimmune disease Guillain-Barre syndrome, that can lead to temporary paralysis.

In the majority of infected individuals symptoms are mild and include fever, skin rashes and flulike illness, according to the World Health Organisation (WHO). Zika virus transmission has been reported in 33 countries. In February WHO declared the Zika virus to be a public health emergency of international concern. The team studied a strain of Zika virus isolated from a patient infected during the French Polynesia epidemic and determined the structure to 3.8 angstrom.

At this near-atomic resolution key features of the virus structure can be seen and groups of atoms that form specific chemical entities, such as those that represent one of 20 naturally occurring amino acids, can be recognised, said researcher Michael Rossmann.

The team found the structure to be very similar to that of other flaviviruses with an RNA genome surrounded by a lipid, or fatty, membrane inside an icosahedral protein shell. The strong similarity with other flaviviruses was not surprising and is perhaps reassuring in terms of vaccine development already underway, but the subtle structural differences are possibly key, Sirohi said.

Most viruses don’t invade the nervous system or the developing foetus due to blood-brain and placental barriers, but the association with improper brain development in foetuses suggest Zika does, Sirohi added.

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